Funds are requested for the purchase of a plasma-desorption time-of-flight mass spectrometer to be shared by several NIH supported users. While several versions of this type of instrument have been built in university laboratories, no commercially manufactured instrument currently exists in a US laboratory. This relatively inexpensive instrument will provide high sensitivity, rapid assessment of molecular weights, and in some cases sequence information, from mass analysis of molecular and fragment ions of biomolecules. The instrument will be used to determine the molecular weight and sequence of modified model decanucleotides to verify their synthesis and homogeneity, to observe microheterogeneity of phosphorylated glycolipids from bacteria, for interspecies comparisons of peptide hormones (relaxins) and transition metal binding proteins, and to determine the sialic acid content and ceremide heterogeneity in gangliosides. In addition, the project will evaluate the capabilities of the instrument for different classes of compounds and for extending the mass range of mass spectrometry, as well as its ruggedness, ease of use and suitability of operation by non-specialists after short term instruction.